Process of preparing arc-lamp electrodes.



G. M. LITTLE & B. J. GUDGE. PROCESS OF PREPARING ARC LAMP ELECTRODES. APPLICATION FILED APR.2I. 910.

1,138,674. Patented May 11, 1915.

WITNESSES:

' A-TTORNEY dTTEe ernir on.

GEORGE IM'. LITTLE, 0F ZPIT'ISBURGH, AND BENJAMIN J. GU'DGE, OF WILKINSBURG- rnnnsrtvnnm, assurances r0 urnsrmonousn ELECTRIC nunrunuuraorunme COMPANY, A CORPORATION Q35 PENNtSYLVANIA.

PROCESS 0F PREPARING ARC-LAMP ELECTRODES.

releases.

Application filed April 21, 1910. Serial 1i 0, 556,880,.

To all whom it may concern and BENJAMIN J, Genet, citizens of the United States, and residents,- respectively,-

of Pittsburgh and Nilkinsburg, both in the county of Allegheny and State of Pennsylvania, have invente a new and useful Improvement in Processes of Preparing Arc- Lamp Electrodes, of which the following is a specification.

Our invention relates to the preparation of arc lamp electrodes, and it has for its.

object toprovide a process of treatment which will produce straight and compact finished electrodes of-unitorm texture and size. v

Figure 1 of the accompanying drawing is a side View of. an even that is employed in practisingour invention, and Fig. 2 represents a finished electrode. While the invention is not limited, in its application, to electrodes of any spcilic composition, it is intended primarily for the treatment of electrodes containing one or more metallic oxide, such as magnetic oxid of iron, titanium oxid, and chromium oxid, which electrodeshave heretofore been prepared by mixing the constituents in a dry, powdered condition, and then packing them in iron tubes.

a For the purpose of practising the pr sent invention, the electrode com-position is some what-different "from those that have heretofore been employed, the change belng made in order to adapt the composition to be pressed or squirted through dies, or to be.

otherwise molded, and to render the finished electrodes strong and durable Without the use of iron containing tubesfor the mixed materials.

A suitable composition is approximately as follows: parts, by weight, of magnetic oxid of iron (Fe O 27 parts of titanium oXid (TiO,), 9 parts of ferrous chromite (Cr O,.FeO), .5 parts of sodium fluorid (NaFl), 1 to 2 parts of starch, or of glucose, or of both, 11} parts of boracic acid, a small 'auantity of summer oil or other suitable oil.

The magnetite, titanium oxid, ferrous chromite, sodium fiuorid and vboraeic acid are first intimately mixed While in a duy powdered condition, and then the starch and glucose, in a Water solution, which has been cocked until the White color has disappeared v and the summer oil are addedQv After an. Be it known that We, GEOfiGElt i, LITTLE other thorough mixing of the ingredients,

Specification of Letters Patent. :Patenfigfl 1W 1i igi li squirting through dies, or for being other? ,1

Wise'molded.

-After. the electrodes are squirted or.

molded, they are baked and hardened by, j passing them through a furnace, or 0ven,'a r simple but suitable and practical form of which is illustrated in Fl 1. The furnace comprises a confined chamber through which extends a tube 1 that is adapted to be rotated V i by means of a pulley 2, which receives power N from anysuitable source, through a belt The tube 1 is heated Within the furnace, dur'w I mg. its rotation, by means of a series of gas flames, WlllCll are adjusted so that the lets. L.

hand end of the tube is black, the middle a bright red, and the right-hand end :tades gradually from bright red to a black.

The green or unbaked electrodes are fed into the left-hand end of the tube, and are moved through, the tube at such a rate as to i be gradually heated tea degree sufficient to carbonize the starch,- and to sinter the re- 8.0 are then gradually cooled,.andareremovedL or discharged from the right-hand end after mainingniaterials together. i The electrodes having been cooled sufficiently to become set. I

A blast of air is directed into the right-hand.

end of the tube, over and around the elec-= trodes as they pass through the tube, and the; carbonaceous gases that are glven off during the baking process will be carried out of the tube at its entrance end, and will not be permitted to remain in the chamber where the electrodes are being bakedandcooled,v thi'sbeing for the purpose of preventing the baking and c oling electrodes from" absorbs. ing any of he carbonaceous ,gases. The,

stream of air also provides oxygen forthe. substantially complete oxidation of the car--;- 1

bon in the electrode. As the tube 1 is some 7 What larger in diameter than the electrodes,

7 the latter Will be rolled, While rendered soft and'pliableby the heat, sothat, irrespective of sufficient length to permit of cooling the electrodes to such a degreethat they are of their condition when fed into the tube,

no longer soft or pliable whenthey are dis charged therefrom.

In order to improve the conductivity of the baked electrodes, they are preferably provided with iron cores, as by the insertior. of iron rods or wires in aXial longitudinal holes that are provided therein, a completed electrode of'this character being shown in Fig. 2, though other suitable means may be employed, if desired, for effecting the same result.

The baking of the electrodes inla draft of air is regarded as an important step in the process of treatment, for the reason that the carbonaceous gases, that are given off during thebaking, are thereby carried away and are prevented from being again absorbed into the electrodes, and the oxygen of the air.

oxidizes and removes substantially all of the carbon, it being desirable that electrodes of this character should contain but a very small percentage, or substantially no carbon. The process of treatment is novel in this respect, since electrodes have heretofore been baked in a carbonaceous atmosphere for the purpose of hardening them. If carbonaceous gases are absorbed into the electrodes, the electrodes will swell and will be materially larger than when in a green or unbaked 'condition, and they are, therefore, mechanically weaker, less compact and less uniform, both in tcxtureand size, than when the carbonaceous gases are driven off gradually and are prevented from being again absorbed into them. It should be noted also that the starch is used only as a temporary binder for the other constituents of the mixture, and is used in the smallest practicable quantity in order .that the finished electrodes may contain substantially no carbon, or at least not suflicient to render them objectionably brittle. It is used for binding together the other constitucuts of the electrodes only while they are in a green or unbaked condition, and for the purpose of facilitating the preliminary me chanical handlin thereof. The baking of the electrodes car onizes, oxidizes and drives out the starch and causesthe other constitucuts to sinter or fuse to ether, and their own binding qualities are tierea-fter relied upon alone for permanently securing them to gether.

Another distinct advantage of the present process of treatment over other processes is, ,that it permits of the employment of a continuously operating furnace, it bein obvious from the above description and from the illustration, that there need be no interruption of the baking operation.

It will, of course, be understood that the process is not limited to the treatment of electrodes having the specific composition that has been described, but that it is applicable generally to the treatment of electrodes of any desired and suitable composition. Also, that the means for practising the invention may be greatly modified from What is illustrated without departing from. the spirit and scope of our invention.

lVe claim as our invention:

1. The process of preparin rod-like electrodes which consists in simu taneously baking and axially rotating them.

2. The process of preparing rod-like elec: trodes containing a volatile binder which consists in simultaneously baking and axially rotating them in air.

3. The process of preparing rod-like elec trodes containing a volatile binder which consists in simultaneously baking and axially rotating them in a draft of air.

4-. The process of preparing rod-like electrodes containing a volatile binder which consists in moving them into and out of a furnace, axially rotating them during such movement, and directing a draft of air upon them while disposed in the furnace.

5. The process of preparing electrodes which. consists in simultaneously baking them, rotating thefn, and removing the carbonaceous gases that are liberated.

6. The process of preparing electrodes which consists in mixing titanic material with a temporary binder, driving out the bindeig and sintering the titanic material while rotating the electrodes.

7. The process of preparing electrodes which consists in mixing titanic material with starch, driving out the starch, and sintering the titanic material while rotating the electrodes.

8. The process of preparing electrodes which consists in mixing titanic material with starch and baking the same while rotating the electrodes.

' 9. The process of preparing rod-like electrodes which consists in bakin and axially rotating them while supported throughout their lengths.

10. The process of preparing rod-like electrodes containing a volatile binder which consists in simultaneously baking and axially rotating them in a draft of air while sup ported throughout their lengths.

In testimony whereof, we have hereunto subscribed our names this 14th day of April, 1910.

O'rro S. SCHAIRER, B. B. Hmas. 

